1. Field of the Invention
This invention pertains to folding tables, and more particularly to folding tables having means to assist the folding and unfolding operations.
2. Description of the Prior Art
Tables comprising two normally horizontal top sections hinged together for folding transversely into two generally parallel and vertical sections are well known. The principal advantage of such tables is that, in the folded condition, they occupy little floor space. The tables may include seating assemblies which fold and unfold together with the table top sections. Exemplary apparatus combining a table and seating arrangement is disclosed in U.S. Pat. No. 3,715,143.
Folding tables must withstand heavy use, so they are sturdily constructed. In addition, many applications of folding tables such as for cafeterias, either with or without seating assemblies, require large sizes. Accordingly, folding tables necessarily are quite heavy, and it normally requires considerable effort to fold them. Uncontrolled opening of a heavy folded table may cause considerable damage to the table and injury to the person operating the table.
To facilitate folding and unfolding large and heavy folding tables, counterbalance mechanisms of various types are commonly employed. U.S. Pat. No. 3,337,262 shows a pair of adjustable coil springs in conjunction with a folding table. U.S. Pat. No. 3,101,062 shows a hydraulic cylinder including a spring for assisting the closing movement and for cushioning the opening movement. The mechanisms of the U.S. Pat. Nos. 3,101,062 and 3,337,262 patents are attached to the hinges joining the table top sections; thus, their weights are added to the mass which the operating person must raise and lower. In addition, the springs do not exert a uniform force throughout the folding and unfolding operations.
The folding table of U.S. Pat. No. 3,715,143 employs torsion bars to assist the operating person raise and lower the table described therein. Although torsion bars possess several desirable features, they nevertheless have some deficiencies. These include non-uniform force through a folding and unfolding cycle, heaviness, and the necessity of heavy anchoring points for the bars. Another drawback of prior counterbalance mechanisms is the inability to construct them so they are interchangeable to suit a variety of table sizes and weights.
Thus, a need exists for a folding table having a counterbalance device which does not add to the weight of the members to be lifted and which exerts a constant force during all stages of folding and unfolding.